Question

我正在尝试使用'weights'数组来填充下面的获取请求图表。但我收到错误“无法使用'NSNumber'类型的参数调用'init'，我不知道为什么。'weights'数组应该是一个UInt16数组。

var weights : [Int16] = []


func weightFetchRequest() -> NSFetchRequest {
            let appDelegate = UIApplication.sharedApplication().delegate as AppDelegate
            let managedContext = appDelegate.managedObjectContext!
            let fetchRequest = NSFetchRequest(entityName: "Assessment")
            fetchRequest.sortDescriptors = [NSSortDescriptor(key: "nsDateOfAssessment", ascending: true)]
            var error: NSError?

            let fetchedResults = managedContext.executeFetchRequest(fetchRequest, error: &error) as [Assessment]?

            if let assessments = fetchedResults {
                let weightss = assessments.map { assessment in assessment.weight }

                weights = weightss

                println(weights)
                println(weightss)
            }
            return fetchRequest
        }

func lineChartView(lineChartView: JBLineChartView!, verticalValueForHorizontalIndex horizontalIndex: UInt, atLineIndex lineIndex: UInt) -> CGFloat {
        if (lineIndex == 0) {
            return CGFloat(weights[Int16(horizontalIndex)] as NSNumber) //Error here
        }
        return 0
    }

Answer 1

行中有两个问题

return CGFloat(weights[Int16(horizontalIndex)] as NSNumber)

weights[Int16(horizontalIndex)]无法编译，因为Int16 不能是数组下标。它应该是weights[Int(horizontalIndex)]。
weights[...] as NSNumber无法编译，因为固定大小整数类型与NSNumber之间没有自动桥接，它应该是NSNumber(short: weights[...])。

所以这将编译和工作：

return CGFloat(NSNumber(short: weights[Int(horizontalIndex)]))

但是，不需要在它们之间使用NSNumber，它可以简化为

return CGFloat(weights[Int(horizontalIndex)])

无法使用“NSNumber”类型的参数调用“init”（Swift）

1 个答案: